Maybe a solution could be weighting the vote according to the user history: a user leaving a single vote on a single movie shouldn't be as influential as an user that voted on a wider range of movies over time
The most obvious effect is movies that drop in the rankings 30 days after release; people who just saw a movie give it 10/10 and then stop participating, so 30 days later they are no longer considered 'active' and their vote stops contributing to the overall ranking.
If someone only gives 10s or 1s to everything, their vote of 10, should probably have less weight, than someone who distributes their votes more evenly.